As an example of known eye open state determination device, an eye open state determination device shown in Patent Literature 1 has been known. The eye open state determination device (eyelid detection device) in Patent Literature 1 includes an image acquisition unit, an eyelid detection unit, and a red eye detection unit. The image acquisition unit acquires a face image. The eyelid detection unit detects upper and lower eyelids from the face image on the basis of an edge serving as a light-dark border. The red eye detection unit senses a spatial light-dark change in an iris portion from the face image to detect a red eye phenomenon, in which light incident on a pupil is reflected by a choroid coat layer in an eyeball and projected on the face image. When the red eye phenomenon is detected by the red eye detection unit, the eyelid detection unit excludes the edge of the pupil associated with the red eye phenomenon from candidates for the edges of the actual upper and lower eyelids.
When a red eye phenomenon described above occurs, the edge of the red eye pupil can be a candidate for the edge of the upper or lower eyelid. Consequently, the edge of the red eye pupil may possibly be determined as the edge of the actual upper or lower eyelid. For example, when an edge appearing over the red eye pupil is determined as the edge of the lower eyelid, it may be erroneously determined from the positional relationship with the edge of the actual upper eyelid that an eye is open. Thus, the red eye phenomenon serves to disturb the determination of the eyelids.
Accordingly, in the eye open state determination device in Patent Literature 1, the edge of the pupil resulting from the red eye phenomenon is excluded from candidates for the edges of the upper and lower eyelids so that the edges of the actual upper and lower eyelids can be correctly recognized and an eye open state can be reliably determined.